The present invention relates to the input subsystem of an electronic large area writing system. More specifically, the invention relates to techniques for correcting input location information to produce a position location indicator on an interactive system, wherein multiple persons may work together for supplying and receiving information with a single large area display. The invention incorporates improved methods for correcting a position location indicator by normalizing input data over frequency and electronic signal drift, and calibrating the input and screen data, and correcting the position location indicator for jitter in the movement of the input device.
In a collaborative working environment, several users may wish to view and manipulate displayed information simultaneously. It is desirable to provide a large area display system measuring several feet across (both horizontally and vertically) comprising a large area rear-projection display system and a position detecting receiving system based upon a position sensing integrating detector. Each of the multiple users would manipulate input devices which could be used simultaneously and independently for controlling its related position location indicator on the display in order to position a cursor, select an item from a menu, draw upon the display screen, or perform any number of standard functions. In this way the actions of each user would be readily visible to all the members of the group who would interact together much as they would relative to a chalkboard or whiteboard.
Computer systems generally incorporate a position location indicator for providing a visual indication to the user of selected data. A specific position location indicator, such as a pointer, may be moved by the user to any desired point on the display in order to locate a cursor for the entry of keystroke characters, to trace the locus of points as in drawing alphanumeric characters or other patterns, to invoke and manipulate a functional command such as paint or erase, to open a menu, to invoke a displayed command, or to invoke other interface functions. In each case the location of the pointer must be known, and in many applications the desired control function should be known as well.
A large area writing system is described, for example, in copending, coassigned U.S. patent application Ser. No. 07/863,650 (Attorney Docket No. D/90106Q) of S. A. Elrod et al., entitled "LARGE AREA ELECTRONIC WRITING SYSTEM," filed Apr. 3, 1992. An input system is described in copending, coassigned U.S. patent application Ser. No. 07/608,439 of S. A. Elrod et al., entitled "POSITION AND FUNCTION INPUT SYSTEM FOR A LARGE AREA DISPLAY," filed Nov. 2, 1990.
Pointer positioning in the above-described system is effected by a user-controlled light-emitting pen which projects a diffuse light spot upon a light-dispersive display screen. The receiving system electronics detects the centroid of the light spot and produces voltages which are related to the input location, and computes input data coordinates from these voltages. However, these coordinates are dependent upon the electronics response of the system and the frequency of the input device, and have a non-linear relationship to the screen coordinates of the display. Information concerning the input data coordinate location for the centroid of the light spot is relayed to the computer system, which determines the screen coordinates that correspond to the sensed input coordinates. The computer system then provides a position location indicator, such as a cursor in the display information, responsive to the input location information. It is an object of this invention to provide a method for correcting the position location indicator for the response of a large area display system to input location information.